Research Article
Vibrational Study and Force Field of the Citric Acid Dimer Based on the SQM Methodology
Table 1
Observed and calculated wavenumbers (cm−1) and assignments for citric acid dimmer.
| Experimentala | Monomerb | Dimera | IR | Raman | IR | Raman | Assignment | SQMc | Assignmenta |
| | 3535 vw | | | O–H | 3537 | ν O33–H39 | | 3535 vw | | | O–H | 3527 | ν O3–H4 | 3498 s | | | | O–H | 3527 | ν O19–H21 | | 3480 vw | | | O–H | 3525 | ν O40–H42 | 3446 m | 3446 vw | | | | 3482 | ν O13–H14 | 3350 sh | 3342 vw | | | | 3470 | ν O31–H35 | 3291 s | 3276 vw | | | | 3066 | O22–H24 | 3247 sh | | | | | | | 3040 sh | | | | | | | 3035 sh | | | | | 3012 | νa CH2 op | 2994 w | 2996 w | | 3000 | a CH2 | 3009 | νa CH2 op | 2994 w | 2996 w | | | | 3006 | νa CH2 ip | 2994 w | 2996 w | | 2975 | a CH2 | 3003 | νa CH2 ip | | 2982 m | | | | 2952 | νs CH2 ip | | 2982 m | | 2950 | s CH2 | 2951 | νs CH2 ip | | 2982 m | | 2934 (21) | s CH2 | 2946 | νs CH2 op | 2950 w | 2961 w | | | | 2945 | νs CH2 op | 2933 w | 2929 m | | | | 2942 | O10–H12 | 1756 vs | | | | | 1786 | νs C=O1 | 1745 sh | 1750 w | | | | 1783 | νs C=O2 | | 1735 s | | | | 1775 | νa C=O2 | | 1735 s | | | | 1771 | νa C=O1 | 1708 vs | 1708 w | 1706 s | 1736 (10) | C=O | 1726 | νa C=O3 | 1698 sh | 1693 vs | 1695 sh | 1693 (11) | C=O | 1677 | νs C=O3 | | 1493 vs | | | | 1483 | δs COH | | 1469 w | | | | 1463 | νa C–C2 | 1430 m | 1432 m, br | 1427 s | 1425 m | δCH2, | 1447 | ν C29–C30 | δCH3 | 1430 m | 1432 m, br | | | | 1430 | δCH2 ip | | 1424 sh | | | | 1426 | δCH2 ip | 1420 sh | | | | | 1417 | δCH2 op | | 1413 w | | | | 1412 | δCH2 op | 1389 m | 1391 s | 1389 s | 1389 (9) | δ COH, | 1402 | δa COH | wag CH3 | 1389 m | | | | | 1385 | wag CH2 op | 1389 m | | | | | 1383 | δC8–O13–H14 | | 1365 w | | | | 1381 | wag CH2 ip | 1358 w | | 1350 w | 1350 w | τCH2 | 1352 | ρCH2 ip | 1340 sh | 1347 w | 1325 vw | | wag CH2 | 1334 | δs COH | 1308 w | | | | | 1308 | δs COH | 1308 w | | | | | 1306 | wag CH2 ip, δC38–O40–H42 | 1308 w | 1301 vw | | | | 1303 | δa COH | 1292 w | 1291 vw | | | | 1303 | ρCH2 ip, wag CH2 ip | | 1285 vw | 1280 w | | δ COH, | 1289 | ρCH2 op | wag CH3 | | 1256 vw | | | | 1266 | νa C–O | 1242 m | | | | | 1258 | νs C–O | 1214 m | 1229 w | | | | 1219 | ρCH2 ip | 1214 m | 1211 m | 1210 w | 1205 s | τCH2 | 1212 | ρCH2 op | 1199 sh | 1201 w | 1195 w | | C–O | | | 1174 s | 1179 w | 1175 s | | δ COH | 1169 | ν C30–O33 | | 1167 w | | | | 1155 | ν C18–O19 | 1140 s | | 1141 s | 1141 (3) | C–O | 1145 | ν C38–O40 | 1140 s | 1140 w | | | | 1140 | ν C1–O3 | 1140 s | 1130 w | | | | 1127 | ν C8–O13 | 1081 w | 1083 m | 1090 w | 1080 s | C–C | 1112 | δa COH | | 1053 m | 1053 m | 1053 (6) | C–C | 1059 | ν C8–C5, ν C8–C15 | 1051 w | | | | | 1057 | ν C29–C32, ν C29–C26 | | 1036 sh | | | | 1039 | wag CH2 op | | 1036 sh | | | | 1036 | τwCH2 op | | 966 vw | | | | 926 | νs C–C2 | 945 w | 943 vs | 943 m | 943 (20) | C–O | 911 | νs C–C1 | | 914 sh | | | | 886 | τwCH2 op | 904 w | 904 m | | | | 885 | τwCH2 op | 904 w | 904 m | | 900 m | C–C | 872 | ν C29–O31 | 881 w | 886 w | | | | 871 | τwCH2 ip | | 867 vw | | | | 865 | τ(O22–H24), τ(O10–H12) | | 850 vw | | | | 857 | ν C32–C38 | | 842 vw | | | | 842 | νa C–C1 | | 842 vw | | | | 827 | γa (OH–O)# | | 807 vw | | | | 800 | δCCC op | | 795 sh | 810 w | | | 792 | γCOO2 | 781 s | 784 vs | | 786 (29) | C–C | 783 | δCOO2 | 729 sh | 723 w | | | | 735 | δCOO5 | | 700 w | | | | 685 | δCOO4 | 686 w | | | 687 (6) | COO | 674 | γCOO5 | | 666 vw | | | | 672 | γCOO3 | | 656 sh | 660 sh | | | 655 | γCOO2 , τ(O3–H4), | τwCH2 op | 640 w | 642 w | 645 w | 645 w | τ(OH) | 637 | τ(O40–H42) | | 627 vw | | | | 631 | τ(O3–H4) | | 627 vw | | | | 625 | τ(O19–H21) | | 627 vw | | | | 621 | δCOO3 | 599 s | 597 w | 598 s | 598 (5) | τ(OH) | 616 | τ(O40–H42), δCOO5, | δC31–C29–C30, ρCOO5 | | 574 w | | | | 574 | δCOO6 | | 571 w | | | | 566 | γCOO4 | 550 w | 559 m | | 556 (7) | τ(OH) | 544 | ρCOO2 | | 541 w | | | | 537 | δCOO1 | 520 sh | 528 vw | | | | 519 | γCOO6 | | 514 w | | | | 499 | γCOO3 , τwCH2 ip, | τ(O19–H21) | 504 w | 509 sh | 503 w | | | 496 | γCOO1 | | 492 vw | | | | 490 | τ(O33–H39) | 477 sh | 476 vw | | | | 485 | γCOO6 | 438 vvw | 453 w | | | | 412 | ρCOO4 | | 415 w | 420 w | | δCOO | 398 | τ(O31–H35) | | 397 w | 392 s | 383 (11) | τ(OH) | 390 | δC31–C29–C26 | | 382 m | | | | 387 | τ(O13–H14) | | 367 w | | | | 373 | ρCOO3, ρCOO1 | | 367 w | 358b | | δ COO | 368 | ρCOO5 | | 348 w | 334b | | δ COO | 345 | ρCOO6 | | 323 vw | 320b | | δ CCO | 329 | δC13–C8–C5 | | 306 w | | | | 294 | δC13–C8–C9 | | 306 w | | | | 271 | δC26–C29–C32 | | 266 w | | | | 251 | δC31–C29–C30 | | 254 sh | 255b | | ρCCC | 236 | δC5–C8–C15 | | 247 vw | 245b | | δ CCC | 222 | δC9–C8–C5 | | 237 vw | 223b | | δ CCC | 221 | δC31–C29–C32 | | 217 w | 187b | | δ CCC | 180 | δC26–C29–C30 | | 212 w | | | | 174 | δCCC op | | | 140b | | | 148 | νs(O–H–O)# | | | | | | 127 | τwCOO3 | | | | | | 122 | δ(OH–O)# | | | | | | 118 | τwCOO5 | | | 105b | | δ CCC | 108 | νa(O–H–O)#, δCCC ip | | | | | | 99 | τwCOO5 | | | 88b | | τwCOO | 92 | δCCC ip | | | 68b | | τwCOO | 72 | τwCC ip | | | | | | 57 | τCC2 | | | | | | 53 | τwop# | | | 44b | | τwCOO | 46 | τwCC op | | | 39b | | τwCOO | 38 | τwCOO1 | | | | | | 32 | τwCOO6 | | | | | | 30 | τwCOO2 | | | | | | 26 | τwCOO1, τwCOO2, | τwCOO3 | | | | | | 25 | τCC1 | | | | | | 11 | γs (OH–O)# | | | | | | 8 | τwCOO4 |
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: stretching; δ: scissoring; wag: wagging; : out-of plane deformation; ρ: rocking; τ: torsion, τw: twisting; a: antisymmetric; s: symmetric; s: strong; m: medium; w: weak; v: very; sh: shoulder; br: broad.
aThis work.
bCalculated by HF/4-21G method from [15].
cTheoretical values from SQM/B3LYP/6-31G* calculations for citric dimer acid. # Intermonomer coordinates.
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